U.S. patent number 5,464,466 [Application Number 08/153,528] was granted by the patent office on 1995-11-07 for fuel storage tank vent filter system.
This patent grant is currently assigned to Gilbarco, Inc.. Invention is credited to Seifollah S. Nanaji, Kenneth L. Pope, Richard R. Sobota.
United States Patent |
5,464,466 |
Nanaji , et al. |
November 7, 1995 |
**Please see images for:
( Certificate of Correction ) ** |
Fuel storage tank vent filter system
Abstract
An apparatus and method for maintaining a desired pressure
within a fuel storage tank or tanks while minimizing or eliminating
the amount of pollutants discharged from the fuel storage tank(s).
A fuel storage tank is provided with a conduit and a chamber
interfaced along the path of the conduit such that all fluid
passing through the conduit must pass through the chamber. A
fractionating membrane is housed within the chamber for capturing
pollutants while allowing air to pass through. As pollutants are
collected on the fractionating membrane, they permeate, thereby
reducing the pressure in the tank and associated conduit. A vapor
pump is provided for drawing vapor through the conduit and the
membrane, and for drawing pollutants off of the membrane. A
pressure transducer located in the tank or associated piping makes
the vapor pump responsive to the pressure therein. A vent is
further provided for allowing air into the tank and piping and for
depressurizing the tank and piping. The apparatus of the present
invention may be provided with a conduit for returning the
pollutants to the fuel storage tank(s).
Inventors: |
Nanaji; Seifollah S.
(Greensboro, NC), Pope; Kenneth L. (Walkertown, NC),
Sobota; Richard R. (Kernersville, NC) |
Assignee: |
Gilbarco, Inc. (Greensboro,
NC)
|
Family
ID: |
22547599 |
Appl.
No.: |
08/153,528 |
Filed: |
November 16, 1993 |
Current U.S.
Class: |
95/45; 95/19;
95/50; 96/4 |
Current CPC
Class: |
B01D
53/22 (20130101); B67D 7/0476 (20130101) |
Current International
Class: |
B01D
53/22 (20060101); B67D 5/01 (20060101); B67D
5/04 (20060101); B01D 061/00 () |
Field of
Search: |
;95/19,45,46,47,54,50
;96/4,6 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0247585 |
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Dec 1987 |
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EP |
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0443068A1 |
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Aug 1991 |
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EP |
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8702074.2 |
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Apr 1987 |
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DE |
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3708950 |
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Sep 1988 |
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DE |
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3806107A1 |
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Aug 1989 |
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DE |
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3824400A1 |
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Jan 1990 |
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DE |
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4142411C1 |
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May 1993 |
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DE |
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9205552.4 |
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Aug 1993 |
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DE |
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4214424 |
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Oct 1993 |
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DE |
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4214551 |
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Oct 1993 |
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DE |
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4225170A1 |
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Feb 1994 |
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DE |
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52-138479 |
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Nov 1977 |
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JP |
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1-270909 |
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JP |
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1341052 |
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Dec 1973 |
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GB |
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668875 |
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Jun 1979 |
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SU |
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WO91/01177 |
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Feb 1991 |
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WO |
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WO91/06363 |
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May 1991 |
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WO |
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WO93/22031 |
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Nov 1993 |
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WO |
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Other References
Magazine: "Das Magazin for Wirtschaft, Forschung, Technik, Umwelt"
Article Entitled: "Kohlenwasserstoffe aus Gasstromen abtrennen" by
Von K. Ohlrogge, dated Jun. 1993. .
A Reprint from "Separation Science and Technology" Article
entitled: "Engineering Aspects of the Plant Design to Separate
Volatile Hydrocarbons By Vapor Permeation" by K. Ohlrogge, J.
Brockmoller, J. Wind, D. Behling, dated 1992. .
Paper entitled "Small Scale Applications to Separate Organic Vapors
by Means of Membranes" by K. Ohlrogge and J. Wind undated. .
Paper entitled "Gossler--Regas Systems" Author unnamed-Undated.
.
paper Presented at "The 1993 Eleventh Annual Membrane
Technology/Separations Planning Conference" Oct. 11, 12, 13, 1993
Newton, Massachusetts entitled Volatile Organic Compound Control
Technology By Means of Membranes by K. Ohlrogge. .
Paper Presented at "The 1991 Annual Membrane Technology/Planning
Conference"0 Nov. 4-6, 1991 Newton, Mass. entitled Operating
Experience with membrane Systems in Gasoline Tank Farms by K.
Ohlrogge..
|
Primary Examiner: Bushey; C. Scott
Attorney, Agent or Firm: Rhodes, Coats & Bennett
Claims
We claim:
1. A method of reducing vaporous fuel emissions from a liquid fuel
storage tank having an upper portion in which fuel vapors are
stored comprising:
connecting the upper portion of the tank to a space bounded on at
least one side with a membrane having the property of permitting
fuel vapor to permeate therethrough,
providing an exit from the space to atmosphere,
holding liquid fuel in the tank and a mixture of vaporous fuel and
air in the upper portion of the tank above the liquid, and
permitting gaseous phase components in the tank to pass to the
space so air passes across the membrane to atmosphere and fuel
vapor permeates through the membrane within the space to reduce the
volume of gasoline and air held in the space and tank and thereby
reduce the pressure in the tank.
2. A method as claimed in claim 1 further comprising returning
permeated fuel vapor to the tank.
3. An apparatus for reducing vaporous fuel emissions comprising
a fuel storage tank having an upper portion in which fuel vapors
and air are stored;
a conduit leading from the upper portion of the tank;
a chamber having
an inlet for receiving vapors and air from the conduit,
a first outlet for the release of air,
a filter element including a membrane having the property of
permitting vaporous pollutants to permeate therethrough, and
a second outlet partitioned from the inlet by the membrane for
receiving fuel permeated through the membrane.
4. An apparatus as claimed in claim 3 wherein said first outlet is
provided with a pressure/vacuum relief valve to atmosphere.
5. An apparatus as claimed in claim 3 further comprising a vacuum
pump between said membrane and said tank to provide a reduced
pressure path through the membrane to induce the vaporous
pollutants to encounter said membrane so as to permeate
therethrough.
6. An apparatus as claimed in claim 5 further comprising a pressure
sensor for said tank and a connection between said pressure sensor
and said vacuum pump, whereby said vacuum pump is turned on when
the pressure in said tank reaches a threshold.
7. An apparatus as claimed in claim 3 wherein a plurality of tanks
are connected to a single chamber through respective conduits.
8. An apparatus for reducing vaporous pollutant emissions from a
plurality of liquid gasoline storage tanks having upper portions in
which gasoline vapors are stored comprising:
a chamber,
conduits leading from upper portions of the tanks to said
chamber,
said chamber having an inlet connected to said conduits, a first
outlet with a pressure/vacuum relief valve towards atmosphere, a
membrane across said chamber and a second outlet, said membrane
having the property of permitting gasoline vapors to permeate
therethrough,
a vacuum pump for said second outlet between said membrane and one
of said tanks to provide a reduced pressure path through the
membrane to induce the gasoline vapors to encounter said membrane
so as to permeate,
a pressure sensor for one of said tanks and a connection between
said pressure sensor and said vacuum pump, whereby said vacuum pump
is turned on when the pressure in said tank reaches a
threshold,
whereby gaseous phase air and gasoline components in the tank may
pass through said conduit to said chamber with air passing across
said membrane to said first outlet and gasoline vapors being
permeated through said membrane within said chamber and exiting
through said second outlet.
Description
Field of the Invention
The present invention relates to apparatus for reducing the
discharge of pollutants from fuel storage tanks, and, in
particular, to a fuel storage tank pressure control system having a
fractionating filter for removing pollutants from vapor discharged
from a fuel storage tank.
BACKGROUND OF THE INVENTION
When fuel is added to a fuel reservoir, such as the gasoline tank
of an automobile from a conventional gas dispenser apparatus such
as the dispensing nozzle of a gasoline dispenser, gasoline vapor is
displaced from the gasoline tank. If the vapor is not collected in
some way, it will be released into the atmosphere. Due to the large
number of automobile refuelings, such releases of fuel vapor
constitute a significant hazard to the environment, particularly in
heavily populated areas. Releases of these vaporst which are
composed of volatile organic compounds (VOC's) such as
hydrocarbons, are presently the subject of significant and
increasing federal and local regulation.
In an effort to guard against the release of volatile organic
compounds to the environment, several systems have been designed to
collect the vapors displaced from automobile gasoline tanks during
refueling. One such system called the "balance" system provides a
rubber boot which surrounds the dispenser nozzle and forms a seal
&round an automobile gasoline tank filler pipe. This system
relies on the volumetric displacement of the vapor by the fluid
transferred through the nozzle to the gasoline tank to force the
vapor through the boot, through a connecting conduit, and back into
a fuel storage tank. A bulky and cumbersome nozzle is required to
effect the necessary seal at the filler pipe. If a perfect seal is
not made, then vapor can leak to the atmosphere instead of being
returned to the storage tank.
To mitigate the need for a cumbersome dispenser nozzle design and
to increase the collection efficiency of the dispenser, systems
have been designed wherein vapor collection at the nozzle is
assisted by a vacuum pump. An example of such a system is disclosed
in U.S. Pat. No. 5,040,577 to Pope, the disclosure of which is
hereby incorporated by reference. A problem that can arise with a
pump assisted system is that the pump can have a tendency to
pressurize the fuel storage tank and associated piping. If the
volume of vapor collected at the nozzle and conveyed into the fuel
storage tank by the vapor pump is more than the volume of liquid
fuel dispensed from the nozzle, the pressure in the fuel storage
tank will be increased. In the current art of vapor pump assisted
vapor recovery systems that use bootless nozzles, a ratio of vapor
recovered versus product delivered greater than 1:1 is required to
achieve desired recovery efficiency at the filler pipe.
Both pressurization and depressurization of the fuel storage tank
can have detrimental effects. When a fuel storage tank has an
internal pressure which is greater than the ambient pressure, there
is an increased tendency for fuel and/or vapor to leak from gaps in
the piping or the tank. Because many tanks are located underground,
it is difficult both to detect leaks and to repair leaks. If the
fuel storage tank becomes highly over-pressurized, there is a
danger that the structural integrity of the tank may be threatened
and even a danger of catastrophic breach of fuel containment.
Additionally, over-pressurization of the fuel storage tank lessens
the efficiency of the vacuum assist pump by creating a greater
pressure differential between the nozzle and the fuel storage
tank.
In order to solve the foregoing problems of over-pressurization,
several devices and methods have been developed to vent fuel
storage tanks. It will be understood that a large portion of gas
vented from the fuel storage tank will consist of volatile organic
compounds. Regulations exist and will likely be made more stringent
which limit the amount of VOC's that may be expelled into the
atmosphere by such vents. Several techniques have been developed to
meet these regulations. One such technique is disclosed in U.S.
Pat. No. 4,118,170 to Hirt. The invention of Hirt involves burning
the vapor vented. The danger of this technique is obvious, and the
technique is presently not allowed in many areas. An alternate
technique is to cool the vapor and return the condensed vapor to
the tank as liquid. This technique is relatively expensive as it
requires a refrigeration device.
Therefore, there exists a need for an efficient, cost-effective
apparatus and method for removing volatile organic compounds and
other pollutants from gas vented from a fuel storage tank.
Furthermore, there exists a need for such a method and apparatus
which can be retrofitted to existing fuel storage tanks.
SUMMARY OF THE INVENTION
The present invention is directed to an apparatus and method for
maintaining a desired pressure within a fuel storage tank or tanks
while minimizing or eliminating the amount or mass of pollutants
discharged from the fuel storage tank or tanks. A fuel storage tank
is provided with a conduit on an upper portion thereof. The conduit
terminates with a vent to the atmosphere. A chamber is interfaced
along the path of the conduit such that all vapor passing through
the conduit must pass through the chamber. A filter or
fractionating membrane is housed within the chamber. Vapor
comprising air and pollutants, such as volatile organic compounds,
traveling through the chamber is separated into each of its two
components by the fractionating membrane. Specifically, the air is
allowed to pass through the chamber, and the pollutants are
captured by the fractionating membrane. A vacuum pump is provided
for drawing pollutants through the membrane and from the membrane.
A pressure transducer located in the tank or associated piping
makes the vapor pump responsive to the pressure therein. When the
tank and piping reach a set pressure level, the transducer actuates
the pump, thereby drawing pollutants through the membrane. The
vapor is removed from the membrane by the pump. A vent is further
provided for allowing air and/or vapor out of the tank and piping
to depressurize the tank and piping if the pump and membrane are
insufficient. The vent can also allow air into the tank to
compensate for any underpressure. The apparatus of the present
invention may be provided with a conduit for returning the
pollutants to one or more of the fuel storage tanks.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be better understood after a reading of the
following description of the preferred embodiment when considered
with the drawings.
FIG. 1 is a schematic view of the vent filter system of the present
invention.
FIG. 2 is a fragmentary, cross-sectional view of the chamber and
the membrane forming a part of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In the following description, like reference characters designate
like or corresponding parts throughout the several views. Also in
the following description, it is to be understood that such terms
as "forward", "rearward", "left", "right", "upwardly",
"downwardly", and the like are words of convenience and are not to
be construed as limiting terms.
Referring now to the drawings in general and FIG. 1 in particular,
it will be understood that the illustrations are for the purpose of
describing a preferred embodiment of the invention and are not
intended to limit the invention thereto.
As best seen in FIG. 1, the fuel storage tank vent system of the
present invention, generally denoted by the numeral 10, is shown
therein in conjunction with two conventional underground fuel
storage tanks 20,30. It will be understood that vent system 10 may
be used with above-ground storage tanks, as well. Furthermore, vent
system 10 may be used with any number of storage tanks. Tank 20
contains high octane fuel and tank 30 contains low-grade fuel. The
preferred embodiment shows the vent system of the present invention
as it may be used with a fuel dispenser system having a vapor
recovery vacuum assist system but it will be understood that the
invention could be used on other vapor recovery systems, such as
the balance system.
Fuel tanks 20,30 have vapor return line 32 for receiving vapor
recovered by a conventional fuel dispenser system having means for
collecting fuel vapors (not shown). Fuel tanks 20,30 further
include fuel delivery lines 24,34 for outputting fuel to the fuel
dispenser. Vent lines 26,36 are provided at the top of tanks 20,30
and extend to manifold 52. The manifolded vent lines 26,36 equalize
the pressure between tanks 20,30, permitting the return of all
vapors to one tank 30 via return line 32. Additional return lines
to additional tanks can be provided but are generally not
needed.
Manifold 52 extends to chamber 50. Chamber 50 has outlet line 56
equipped with vent 59, which is covered by rain shield 58 and has
open and closable pressure/vacuum vent control valve 61. Line 54
connects the lower portion of chamber 50 and tank 30.
Membrane 60 is positioned within chamber 50 such that it separates
chamber 50 into two distinct plenums 50a,50b. Membrane 60 is
preferably a fractionating membrane developed by
GKSS-Forschangszentram Gesthacht GmbH of Germany and described in
"Operating Experiences with Membrane Systems in Gasoline Tank
Farms," presented by K. Ohlrugge at the 1991 9th Annual Membrane
Technology/Planning Conference in Newton, Mass., Oct. 4-6, 1991 or
"Volatile Organic Compound Control Technology by Means of
Membranes," presented by K. Ohlrugge at the 1993 11th Annual
Membrane Technology/Separation Planning Conference in Newton, Mass.
Oct. 11-13, 1993, the disclosures of which are hereby incorporated
by reference. A property of membrane 60 is that it will capture or
collect selected pollutants including hydrocarbons such as gasoline
vapor while allowing air to pass through. As shown, membrane 60 is
configured as a cylinder comprising a plurality of stacked and
bound thin sheets 63. Each sheet 63 has a hole formed its center
such that the cylinder has an aperture disposed therein extending
axially from end to end. Disposed within the aperture is removal
pipe 67 which has perforations 65 formed therein.
In operation, vent system 10 functions as follows. As fuel is
dispensed via a fuel dispenser system (not shown), a given volume
of liquid fuel, V.sub.L, is drained from either tank 20 or tank 30
through either delivery line 24 or delivery line 34, respectively.
Concurrently with the draining of liquid fuel, a given volume of
fuel vapor, V.sub.V, is forced into tank 30 through vapor return
line 32 by the vapor pump (not shown). Typically, the ratio of
V.sub.V to V.sub.L will be greater than 1:1. It will be understood
that, as a result of this ratio, the pressure within the tanks will
have a tendency to become greater than the ambient atmospheric
pressure. It is also possible that the ratio of V.sub.V to V.sub.L
will be less than 1:1. This would result in tank pressures less
than atmospheric.
The pressure in plenum 50b is a design choice. Normally, valve 61
will remain closed. When the pressure in tanks 20,30, and thus
manifold 52 and vent lines 26,36, reaches a given pressure,
pressure transducer 53 causes pump 51 to operate. The actuation of
pump 51 creates a vapor flow from tank 30, through vent line 36,
through chamber 50, and through line 54 to tank 30. As the vapor
flows through chamber 50, it encounters membrane 60. As the fuel
vapor encounters membrane 60, the selected pollutants in the vapor
are captured by the same. The vacuum created by pump 51 draws the
pollutants away from the sheets 63 of membrane 60 and into removal
pipe 67 through the perforations 65 formed in the same. The
pollutants which flow into pipe 67 finally flow through line 54 and
are deposited in low grade tank 30.
When the pressure in the tanks has returned to the desired
pressure, pump 51 is de-actuated, stopping the flow of vapor.
If the system pressure becomes higher than can be sufficiently
reduced by permeating the vapor through membrane 60, valve 61 opens
to allow the vapor to vent to atmosphere. Because the substantial
majority of the pollutants in the vapor are captured by membrane
60, opening of the valve 61 to release pollutants to the
environment should be rare. Because of the physical properties of
membrane 60, it is still preferable to actuate pump 51 to draw the
vapor into pipe 67.
If the tank pressure becomes less than atmospheric, the opening of
valve 61 will return the tank pressure to atmospheric by allowing
air to enter.
Certain modifications and improvements will occur to those
skilled-in the art upon a reading of the foregoing description. It
should be understood that all such modifications and improvements
are properly within the scope of the following claims:
* * * * *